(NECN: Kathryn Sotnik, Andover, Mass.) - The FBI in Boston is offering a reward of up to $20,000 for information leading to the recovery of two weapons stolen from an FBI vehicle.

According to a news release from the Boston Division of the FBI, the Colt M16-A1 rifle and HS Precision Pro-series 2000 Sniper Rifle were stolen from a SWAT vehicle parked in Andover, Mass. Wednesday night into the early morning hours Thursday.

Sallet wouldn't get into specifics about how the thief stole the rifles, or whether the vehicle was broken into, only saying the vehicle was "illegally entered."

"It's an ongoing criminal investigation, so I can't discuss the details of that," said Sallet. "That's why I'm using the term 'illegally entered.'"

The FBI confirms the agent had the vehicle parked at his property when the rifles were stolen.

"There are times where it is permissible by FBI policy by a member of the SWAT team or other special agents to store weapons in a vehicle," said Sallett. "There's a proper protocol as to how those weapons have to be stored and are stored."

That protocol is now under internal review by the FBI, according to Salett.

Sallet would not comment Thursday on the current status of the FBI agent, citing the internal investigation.

Andover Police confirm they investigated thefts around the same time along Canterbury Street in the Shawsheen area of Andover.